feat(VocabLessonView): improve vocab question generation and answer validation

- Introduced a new method to retrieve equivalent vocabulary answers based on user prompts and direction, enhancing the accuracy of answer options.
- Updated the buildChoiceOptions method to handle multiple correct answers and ensure the prompt is excluded from choices.
- Enhanced the current vocab question structure to support multiple acceptable answers, improving user feedback and engagement during exercises.

frontend/src/views/social/VocabLessonView.vue

@@ -1589,11 +1589,30 @@ export default {
       // Starte neue Frage im Multiple Choice Modus
       this.nextVocabQuestion();
     },
-    buildChoiceOptions(correctAnswer, allVocabs, excludePrompt = null) {
+    getEquivalentVocabAnswers(prompt, direction, allVocabs) {
-      const options = new Set([correctAnswer]);
+      const normalizedPrompt = this.normalizeVocab(prompt);
+      const matches = [];
+
+      allVocabs.forEach((entry) => {
+        const source = direction === 'L2R' ? entry.learning : entry.reference;
+        const target = direction === 'L2R' ? entry.reference : entry.learning;
+        if (!source || !target) return;
+        if (this.normalizeVocab(source) !== normalizedPrompt) return;
+        if (!matches.includes(target)) {
+          matches.push(target);
+        }
+      });
+
+      return matches;
+    },
+    buildChoiceOptions(correctAnswers, allVocabs, excludePrompt = null) {
+      const normalizedCorrectAnswers = Array.isArray(correctAnswers) ? correctAnswers : [correctAnswers];
+      const options = new Set(normalizedCorrectAnswers.filter(Boolean));
       // Normalisiere alle Werte für den Vergleich (trim + lowercase)
       const normalizedExcludeSet = new Set();
-      normalizedExcludeSet.add(this.normalizeVocab(correctAnswer));
+      normalizedCorrectAnswers.forEach((answer) => {
+        normalizedExcludeSet.add(this.normalizeVocab(answer));
+      });
       // Wichtig: Der Prompt (die Frage) darf nicht in den Optionen erscheinen
       if (excludePrompt) {
         normalizedExcludeSet.add(this.normalizeVocab(excludePrompt));
@@ -1698,10 +1717,22 @@ export default {
       const randomIndex = Math.floor(Math.random() * sourcePool.length);
       const vocab = sourcePool[randomIndex];
       this.vocabTrainerDirection = Math.random() < 0.5 ? 'L2R' : 'R2L';
+      const allTrainerVocabs = [...this.importantVocab, ...this.vocabTrainerMixedPool];
+      const prompt = this.vocabTrainerDirection === 'L2R' ? vocab.learning : vocab.reference;
+      const acceptableAnswers = this.getEquivalentVocabAnswers(
+        prompt,
+        this.vocabTrainerDirection,
+        allTrainerVocabs
+      );
       this.currentVocabQuestion = {
         vocab: vocab,
-        prompt: this.vocabTrainerDirection === 'L2R' ? vocab.learning : vocab.reference,
+        prompt,
-        answer: this.vocabTrainerDirection === 'L2R' ? vocab.reference : vocab.learning,
+        answers: acceptableAnswers.length > 0
+          ? acceptableAnswers
+          : [this.vocabTrainerDirection === 'L2R' ? vocab.reference : vocab.learning],
+        answer: acceptableAnswers.length > 0
+          ? acceptableAnswers.join(' / ')
+          : (this.vocabTrainerDirection === 'L2R' ? vocab.reference : vocab.learning),
         key: this.getVocabKey(vocab),
         source: questionSource
       };
@@ -1720,8 +1751,8 @@ export default {
         debugLog('[VocabLessonView] Answer:', this.currentVocabQuestion.answer);
         // Wichtig: Der Prompt (die Frage) darf nicht in den Optionen erscheinen
         this.vocabTrainerChoiceOptions = this.buildChoiceOptions(
-          this.currentVocabQuestion.answer, 
+          this.currentVocabQuestion.answers, 
-          [...this.importantVocab, ...this.vocabTrainerMixedPool],
+          allTrainerVocabs,
           this.currentVocabQuestion.prompt // Exkludiere den Prompt
         );
         debugLog('[VocabLessonView] Choice-Optionen erstellt:', this.vocabTrainerChoiceOptions);
@@ -1757,8 +1788,9 @@ export default {
       }
       
       const normalizedUser = this.normalizeVocab(userAnswer);
-      const normalizedCorrect = this.normalizeVocab(this.currentVocabQuestion.answer);
+      const normalizedCorrectAnswers = (this.currentVocabQuestion.answers || [this.currentVocabQuestion.answer])
-      this.vocabTrainerLastCorrect = normalizedUser === normalizedCorrect;
+        .map(answer => this.normalizeVocab(answer));
+      this.vocabTrainerLastCorrect = normalizedCorrectAnswers.includes(normalizedUser);
       
       // Update Stats
       const stats = this.getVocabStats(this.currentVocabQuestion.vocab);